The present invention relates in general to a tightly sealable fold collar or bellows enabling a quick assembly for protecting thereby universal joints, steering and guiding axle couplings, which bellows possesses a longitudinal sealing closure and is particularly suitable for protecting swing axle rotating joints (cardan joints) of motor vehicles.
More in particular the present invention concerns a protective bellows adapted to be quickly installed on a homokinetic "CARDAN" type universal joint of motor vehicles, said bellows comprising two bodies in the form of shell halves which are assembled together by means of a fitting system with simultaneous gluing.
On motor vehicles the bellows covering the cardan joint is of hermetically closed design for grease- and oil tightness such that the joint is protected against damage and corrosion. The conventional CARDAN bellows being constructed as a one-part body necessitates its installing to be carried out simultaneously with the assembly of the universal joint and hence its replacement in case of a defect, for instance a cut or a tear or a porosity leak, compels the operator to entirely take off the cardan joint, which gives rise to a considerable loss of time.
In order to overcome this drawback it has been recommended to manufacture a protective bellows having a sealable closure of the kind with snap-locked jointing edges. Such a bellows allowing rapid installment is known for instance from U.S. Pat. No. 4,558,869.
These models as a whole comprise a lateral opening extending in the longitudinal direction for allowing the entry of the coupling axle without need of disconnecting the cardan joint. They are assembled together by an interlocking system with "U"-shaped edge and matching lip, the hole being sealed by wedding or gluing. The joint of conventional design with "U"-shaped edge and inserted lip has the disadvantage of causing a local overthickness and a sudden change in the rigidity of the bellows body. These jointing closures necessarily have a lower flexibility than that of the bellows shell and as a consequence the latter no longer provides in every direction the same flexibility or fitness to dissipate the alternating compressive and tensile bending stresses when in use.
Moreover temperature variations, particularly in winter when ambient temperatures may be as low as minus 20.degree. C. or even lower, give rise to stiffening of the plastic or elastomeric material of the tubular body, which shows a greatly pronounced increase and variation of ridigity in the region of the closing joint.
In addition to this problem the known bellows generally display an interlocking closure of rather poor design which is not adapted to ensure a sufficiently long service life of the welded or glued joint, and this in the light of the geometry of the interconnected edges and the tenacity of the finished closure. Thus it has been established that known protective bellows are not satisfactory from the viewpoint of durability and watertightness. In normal use conditions the jointing closure itself tends to loosen prematurely. In extreme conditions (low temperatures) the bellows looses at the place of the interlocking closure its elasticity needed withstand high loads occurring when applying full lock upon turning the vehicle, which may make appear fissures through which grease will escape such that the cardan joint is bound to degrade in the long run.
On the other hand the U-shaped interlocking closure extending longitudinally from one bellows end to the opposite end, as shown opened for closing the bellows after the latter has been positioned, must sustain in rainy weather the direct hit of water projected in continuous jets which are augmented by the speed of rotation and hence increase the penetration force of the water. Moreover, the glue used in the gluing step after the interlocking operation exerts a dissolving action upon the interlocked tongue and a welding effect by solvent aided fusion of the material. A drawback thereof consists in the fact that, when the operator doesn't watch carefully the overflowing of the solution, the latter may cause dissolution of the bellows material on places when it's not desirable. As a result perforations may develop at solvent deposit spots, so that the bellows is no longer watertight.
In addition it has to be understood that for adapting the so-called standard system in order to be realizable on all types of European motor vehicles, it's necessary to have different opening diameters available for the bellows, namely one opening end for the wheel side the diameter of which may vary from 66 mm to 91 mm, and likewise for the axle or tube side with a diameter varying from 20 to 40 mm. A disadvantage of existing rapid-assembling protective bellows consists in the absence of opening diameters which are adaptable for vehicles having a diameter which is larger than 81 mm on the wheel side.